Wireless traffic on all wifi routers are protected by a security protocol. It started with WEP (Wireless Equivalent Privacy). It was a very simple protocol, and is easily recognised by its 10 or 26 hexadecimal digits. In 2003, it was announced that WEP had been superseded by an interim and not yet fully ratified standard called WPA (Wifi Protected Access). In 2004, when the standard was fully ratified, a more secure and complex version (WPA2) became the new standard. It had the ability to use industry standard encryption (AES) and work in both a home mode (pre-shared key) and an enterprise mode (authentication server).
This protocol has stood tall until TODAY, 16 October 2017.
When weaknesses were discovered in the previous 2 protocols, there was always a more secure successor in the wings.
Today, Mathy Vanhoef, a security expert at KU Leuven University in Belgium published a report on a flaw he discovered in the protocol. He called it the KRACKs (Key Reinstallation AttaCKs). This flaw is in the heart of the protocol, so it affects each and every implementation thereof.
How it works is fairly simple. When connecting to a wifi network, there is a 4-way handshake between the access point and the client. The client installs the encryption key on the 3rd stage of the handshake. Because of the fickle nature of wireless connections, routers will often re-send the 3rd handshake if they do not receive an acknowledgement from the client. A nefarious eavesdropper (yes, fortunately they have to be in physical proximity to the client) can capture the key, manipulate it and re-transmit it, tricking the client into installing it a second time – and thus resetting the internal protocol sequence counters to 0. With known values and known content, it becomes easy to decrypt data streams and even inject malware into the data stream.
Even more concerning is that some versions of Android and Linux can be tricked into installing an all-zero key, making it trivial to then decrypt and/or manipulate communications.
As inscribed on the front of the Hitchhiker’s Guide to the Galaxy (a sci-fi book by Douglas Adams) – “DON’T PANIC”.
So, what should be considered, and what to do
It is not all doom and gloom, patches should soon be available. It is also not a trivial attack to accomplish. An attacker has to be close to the client, so that although there may be an exploit in the wild, someone would literally have to be sitting in a car outside your house to affect your home wifi. Also, secure communications, viz. those who use HTTPS to encrypt communications, will still be secure. Thankfully, there are a lot of these sites including banks and and popular mail systems. Be sure to check for the padlock in your browser. VPN traffic to and from corporate environments will also still be secure, as well as SSH connections. These protocols employ an additional layer of encryption (not affected by the flaw) over and above the wifi encryption.
An attack is designed to compromise the client, not the access point, so there may or may not be a patch for your router. Vendors were already notified back in July/August so they should be hard at work making fixes.
Mobile phone patches may take some time to come out as they have a long patch lifecycle. After an android patch (for example) is released, it still needs to be ratified and implemented by the hardware vendors and often by the retailers (like mobile phone companies), who then make further customizations before shipping to customers.
Home and small business users should be concerned but not worried. Vendors like Microsoft and others are working on fixes. Users should update their devices as soon as a patch is available.